import java.util.Scanner;

public class demo05 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入整数n:");
        int n = scanner.nextInt();
        System.out.println(jc(n));
    }
    public static int jc(int n) {
        int sum = 1;
        if (n < 0) {
            System.out.println("输入错误！");
        } else if (n == 0 || n == 1) {
            System.out.println( n + "的阶乘为1");
        } else {
            for (int i = 1; i <= n; i++) {
                sum = sum * i;
            }
            return sum;
        }
        return sum;
    }
}